Hatch-Waxman litigation is back on the rise, particularly in the U.S. District Court for the District of Delaware, according to Lex Machina's annual report on litigation involving generic drugs.

Suits filed in response to Abbreviated New Drug Applications (ANDA) were a pocket of strength in an otherwise declining patent litigation landscape. ANDA suits rose 29 percent to 417 in 2017, though that number remains below the 2015 peak of 475 suits, according to the report.

At the Patent Trial and Appeal Board (PTAB), administrative challenges to patents listed in the U.S. Food and Drug Administration's Orange Book were down slightly, from 100 in 2016 to 96 last year.

More than half of the new district court cases were filed in Delaware, where suits rose 60 percent to 241. Branded pharmaceutical companies have been filing more often in Delaware, and a decision from Chief Judge Leonard Stark of the District of Delaware last September limited the venue objections that generics can raise based on the U.S. Supreme Court's TC Heartland decision.

New Jersey remained the second-most popular venue, where filings remained relatively flat at 111 cases. Activity fell in the U.S. District Court for the Eastern District of Virginia from 17 cases to two.

At the PTAB, Administrative Law Judges Tina Hulse, Lora Green and Christopher Paulraj handled the most Orange Book-related petitions.

Eli Lilly and Co., Pfizer Inc. and Sanofi-Aventis U.S. were the companies filing the most ANDA-related challenges in district court over the last two years, according to the Lex Machina data. Morris, Nichols, Arsht & Tunnell had the most district court representations during that period, followed by Finnegan, Henderson, Farabow, Garrett & Dunner and McCarter & English.

Teva Pharmaceutical, Mylan Pharmaceuticals Inc. and Apotex Inc. were the most frequent defendants in district court. The busiest defense firms were Phillips, Goldman, McLaughlin & Hall; Winston & Strawn; and Shaw Keller.

At the Patent Trial and Appeal Board, Wilson Sonsini Goodrich & Rosati; Alston & Bird and Carlson, Caspers, Vandenburgh, Lindquist & Schuman were on the attack most often for generics. Fish & Richardson; Finnegan Henderson; and Williams & Connolly were the most active in defense of patent owners.

The most litigated drugs were Biogen's multiple sclerosis treatment Tecfidera, Bristol-Myers Squibb Co.'s heart medication Eliquis, and Amgen dialysis treatment Sensipar.